Periodic fluctuation of reference evapotranspiration during the past five decades: Does Evaporation Paradox really...

Evidence that the pan evaporation or reference evapotranspiration (ET₀) as the indicator of atmospheric evaporation capability have decreased along with the continuous increase in temperature over the past decades (coined as "evaporation paradox") has been reported worldwide. Here, we provide a nationwide investigation of spatiotemporal change of ET₀ using meteorological data from 602 stations with the updated data (1961-2011). In addition, we explore the trigger mechanism by quantitative assessment on the contribution of climatic factors to ET₀ change based on a differential equation method. In despite of different shift points regionally, our results suggest that the ET₀ generally present decadal variations rather than monotonic response to climate change reported in previous studies. The significant decrease in net radiation dominate the decrease in ET₀ before early 1990s in southern regions, while observed near-surface wind speed is the primary contributor to the variations of ET₀ for the rest regions during the same periods. The enhancements of atmospheric evaporation capability after early 1990s are driven primarily by recent relative humidity limitation in China. From a continental scale view, as highly correlating with to Pacific Decadal Oscillation, the shift behaviors of ET₀ is likely an episodic phenomenon of the ocean-atmosphere interaction in earth.